Limiting system for a vehicle suspension component

ABSTRACT

The damper assembly includes a tubular member, a rod, a primary piston, a secondary piston, and a resilient member. The tubular member includes a sidewall and a cap positioned at an end of the sidewall. The sidewall and the cap define an inner volume. The sidewall includes a shoulder separating the tubular member into a first portion and a second portion. The resilient member is disposed between the secondary piston and the cap and thereby is positioned to bias the secondary piston into engagement with the shoulder.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application is a continuation of U.S. application Ser. No.16/838,391, filed Apr. 2, 2020, now U.S. Pat. No. 11,255,401, which is acontinuation of U.S. application Ser. No. 16/041,229, filed Jul. 20,2018, now U.S. Pat. No. 10,619,696, which is a continuation of U.S.application Ser. No. 15/084,375, filed Mar. 29, 2016, now U.S. Pat. No.10,030,737 which is a continuation of U.S. application Ser. No.13/792,151, filed Mar. 10, 2013, now U.S. Pat. No. 9,303,715, all ofwhich are incorporated herein by reference their entireties.

BACKGROUND

The present application generally relates to vehicle suspension systems.In particular, the present application relates to dampers having asystem to reduce impulse forces as the vehicle suspension systemexperiences a jounce event or a recoil event. Dampers (i.e. dashpots,hydraulic shock absorbers, etc.) dissipate kinetic energy as part of avehicle suspension system. Dampers often include a housing, end caps, apiston, and a rod that is coupled to the piston. Energy is dissipated ashydraulic fluid flows along a hydraulic circuit (e.g., between a firstchamber within the housing to a second chamber within the housing). Thepiston may include a plurality of orifices that are covered with a shimstack having a plurality of compressed shims.

As the piston moves through the housing, hydraulic fluid is forced froma first chamber, through the piston, and into the second chamber.Specifically, pressurized hydraulic fluid is forced through the orificeswithin the piston, deflects a portion of the shims to create an opening,and flows into the second chamber by passing through the opening. Suchtraditional dampers provide damping forces that are constant between afirst end of stroke (e.g., extension) and a second end of stroke (e.g.,compression). Where the vehicle interacts with an obstacle, a force isimparted into the piston through the rod of the damper. The pistontranslates toward an end of the damper and may impart a large impulseforce on the end cap. Such large forces may cause damage to the piston,the end cap, the walls of the housing, or still other components of thedamper assembly. Large impulse forces are also transferred to occupantswithin the vehicle.

Traditional dampers may include a limiting system that absorbs ordissipates energy thereby reducing the impulse forces imparted onoccupants of the vehicle. Some limiting systems absorb and store energy(e.g., using a spring, a gas chamber, etc.) as the piston moves towardthe end of stroke. Such a spring may produce up to 30,000 pounds offorce with one inch of displacement. The stored energy is thereaftertransferred to another component (e.g., the piston, the rod, etc.) asthe piston moves toward the opposing end of the housing. While stillother limiting systems dissipate energy, such systems provide flow pathsthrough flow orifices within the primary piston and along the damperpiston. These limiting systems are susceptible to obstruction due todebris and may generate inconsistent damping forces.

SUMMARY

One embodiment of the present disclosure relates to a damper assembly.The damper assembly includes a tubular member, a rod, a primary piston,a secondary piston, and resilient member. The tubular member includes asidewall and a cap positioned at an end of the sidewall. The sidewalland the cap define an inner volume. The sidewall includes a firstportion fixedly coupled with a second portion of the sidewall. The firstportion and the second portion define a shoulder of the sidewall. Therod extends within the inner volume. The primary piston is positionedwithin the inner volume and coupled to the rod. The primary pistondefines a first contact surface. The secondary piston has a secondcontact surface, an opposing second surface, and an inner cylindricalface that receives the rod. The secondary piston defines a channelextending between the inner cylindrical face and an outer periphery ofthe secondary piston. The primary piston and the secondary pistonseparate the inner volume into a first working chamber, a second workingchamber, and a recoil chamber. The resilient member is disposed betweenthe secondary piston and the cap and thereby positioned to bias thesecondary piston into direct engagement with the shoulder. The firstcontact surface and the channel are configured to cooperatively define aflow conduit upon engagement between the primary piston and thesecondary piston. The second contact surface is configured to engage thefirst contact surface such that an open flow path is formed from therecoil chamber through (i) an aperture of the secondary piston and (ii)the flow conduit, upon engagement between the primary piston and thesecondary piston.

Another embodiment of the present disclosure relates to a damperassembly. The damper assembly includes a housing, a primary piston, anda limiter. The housing has an end cap and defines an inner volume. Thehousing includes a first portion fixedly coupled with a second portion.A transition between the first portion and the second portion defines ashoulder. The primary piston is positioned within the housing. Thelimiter is positioned between the primary piston and the end cap. Thelimiter includes a damper piston and a resilient member. The damperpiston has a contact surface, an opposing second surface, and an innercylindrical face. The primary piston and the damper piston separate theinner volume into a first working chamber, a second working chamber, anda recoil chamber. The resilient member is disposed within the recoilchamber, between the opposing second surface of the damper piston andthe end cap. The resilient member is thereby positioned to bias thedamper piston into direct engagement with the shoulder. The rod iscoupled to the primary piston and extends past the inner cylindricalface. The damper piston defines a channel extending laterally outwardbetween the inner cylindrical face and an outer periphery of the damperpiston across the contact surface. The primary piston and the channelare configured to cooperatively define a first flow conduit uponengagement between the primary piston and the damper piston. An apertureof the damper piston defines a second flow conduit. The first flowconduit and the second flow conduit cooperate to define an open flowpath from the recoil chamber.

Another embodiment of the present disclosure relates to a damperassembly. The damper assembly includes a housing, a primary piston, anda limiter. The housing has an end cap and defines an inner volume. Thehousing includes a first portion fixedly coupled with a second portionof the housing. A transition between the first portion and the secondportion defines a shoulder of the housing. The primary piston ispositioned within the housing. The limiter is positioned between theprimary piston and the end cap. The limiter includes a damper piston, aresilient member, and a rod. The damper piston has a contact surface, anopposing second surface, and an inner cylindrical face. The primarypiston and the damper piston separate the inner volume into a firstworking chamber, a second working chamber, and a recoil chamber. Theresilient member is disposed within the recoil chamber, between theopposing second surface of the damper piston and the end cap. Theresilient member is thereby positioned to bias the damper piston intodirect engagement with the shoulder. A rod is coupled to the primarypiston. The damper piston defines a channel and an inner channel. Thechannel extends laterally between the inner cylindrical face and anouter periphery of the damper piston across the contact surface. Theprimary piston and the channel are configured to cooperatively define aflow conduit upon engagement between the primary piston and the damperpiston. The flow conduit and the inner channel cooperate to define anopen flow path from the recoil chamber.

The invention is capable of other embodiments and of being carried outin various ways. Alternative exemplary embodiments relate to otherfeatures and combinations of features as may be recited in the claims.

BRIEF DESCRIPTION OF THE FIGURES

The disclosure will become more fully understood from the followingdetailed description, taken in conjunction with the accompanyingfigures, wherein like reference numerals refer to like elements, inwhich:

FIG. 1 is an elevation view of an axle assembly, according to anexemplary embodiment.

FIG. 2 is an elevation view of a suspension system, according to anexemplary embodiment.

FIG. 3 is an elevation view of a damper having a limiter that dissipatesenergy, according to an exemplary embodiment.

FIGS. 4A-4D are elevation views of a damper in various stages ofcompression, according to an exemplary embodiment.

FIG. 5 is an elevation view of a damper assembly, according to anexemplary embodiment.

FIGS. 6-11 are partial sectional views of a damper assembly having arecoil damper in various stages of compression, according to anexemplary embodiment.

FIG. 12 is an elevation view of a secondary plunger having a dampinggroove, according to an exemplary embodiment.

FIG. 13 is a side plan view of a secondary plunger, according to anexemplary embodiment.

FIG. 14 is an elevation view of a portion of a secondary plunger havinga damping groove, according to an exemplary embodiment.

FIG. 15 is a sectional view of a secondary plunger having a dampinggroove, according to an exemplary embodiment.

DETAILED DESCRIPTION

Before turning to the figures, which illustrate the exemplaryembodiments in detail, it should be understood that the presentapplication is not limited to the details or methodology set forth inthe description or illustrated in the figures. It should also beunderstood that the terminology is for the purpose of description onlyand should not be regarded as limiting.

Referring to the exemplary embodiment shown in FIG. 1 , an axle assembly110 is configured to be included as part of a vehicle. The vehicle maybe a military vehicle, a utility vehicle (e.g., a fire truck, a tractor,construction equipment, a sport utility vehicle, etc.), or still anothertype of vehicle. As shown in FIG. 1 , axle assembly 110 includes adifferential 112 coupled to a half shaft 114. As shown in FIG. 1 , halfshaft 114 is coupled to a wheel end assembly 116. The wheel end assembly116 may include brakes, a gear reduction, steering components, a wheelhub, a wheel, a tire, and other features. According to an exemplaryembodiment, the differential 112 is configured to be coupled to a driveshaft of the vehicle. Such a differential 112 may receive rotationalenergy from a prime mover (e.g., a diesel engine, a gasoline engine, anelectric motor, etc.) of the vehicle. The differential 112 thenallocates torque provided by the prime mover between the half shafts 114of the axle assembly 110. The half shafts 114 deliver the rotationalenergy to each wheel end assembly 116. According to an alternativeembodiment, each wheel end assembly 116 includes a prime mover (e.g.,the axle assembly 110 includes electric motors that each drive onewheel).

According to an exemplary embodiment, the axle assembly 110 includes asuspension system 118 that couples the chassis of the vehicle to wheelend assembly 116. In some embodiments, the chassis includes a pair ofopposing frame rails, and the suspension system 118 engages the opposingframe rails through side plate assemblies. In other embodiments, thechassis is a hull, a capsule, or another type of structural member.According to an exemplary embodiment, the suspension system 118 includesa spring, shown as gas spring 120, and a damper, shown as hydraulicdamper 122. As shown in FIG. 1 , the gas spring 120 and the hydraulicdamper 122 are coupled in parallel to a lower support member, shown aslower swing arm 126. According to an exemplary embodiment, the wheel endassembly 116 is coupled to lower swing arm 126 and an upper supportmember, shown as upper swing arm 124.

According to an exemplary embodiment, the vehicle is configured foroperation on both smooth (e.g., paved) and uneven (e.g., off-road,rough, etc.) terrain. As the vehicle travels over uneven terrain, theupper swing arm 124 and the lower swing arm 126 guide the verticalmovement of the wheel end assembly 116. A stop, shown as cushion 128,provides an upper bound to the movement of the wheel end assembly 116.It should be understood that axle assembly 110 may include similarcomponents (e.g., wheel end assemblies, suspension assemblies, swingarms, etc.) for each of the two opposing lateral sides of a vehicle.

Referring next to the exemplary embodiment shown in FIG. 2 , thesuspension system 118 includes various components configured to improveperformance of the vehicle. As shown in FIG. 2 , gas spring 120 is ahigh pressure gas spring. According to an exemplary embodiment, thesuspension system 118 includes a pump, shown as high-pressure gas pump130, that is coupled to gas spring 120. In some embodiments, suspensionsystem 118 includes a plurality of high-pressure gas pumps 130 eachcoupled to a separate gas spring 120. In other embodiments, thesuspension system 118 includes fewer high-pressure gas pumps 130 thangas springs 120. According to an exemplary embodiment, the gas springand the pump include gas made up of at least 90% inert gas (e.g.,nitrogen, argon, helium, etc.). The gas may be stored, provided, orreceived in one or more reservoirs (e.g., tank, accumulators, etc.).During operation, the high-pressure gas pump 130 selectively providesgas, under pressure, to at least one of the gas springs 120 and thereservoir. In some embodiments, at least one of the gas springs 120 andthe hydraulic dampers 122 receive and provide a fluid (e.g., gas,hydraulic fluid) to lift or lower the body of the vehicle with respectto the ground thereby changing the ride height of the vehicle.

According to the exemplary embodiment shown in FIG. 3 , a suspensioncomponent, shown as damper 200 includes a rod, shown as shaft 210,coupled to a body portion 220. As shown in FIG. 3 , body portion 220includes a tubular member, shown as housing 230, that includes a firstend 232 and a second end 234. An end cap 236 is coupled to first end 232of housing 230. Housing 230 includes a sidewall defines an inner volume,and shaft 210 translates within the inner volume between an extendedposition and a retracted position. According to an exemplary embodiment,a piston, shown as plunger 240, is positioned within the inner volume ofhousing 230 and coupled to an end of shaft 210. A limiter, shown asrecoil damper 250, is disposed within the inner volume of housing 230between plunger 240 and end cap 236. Recoil damper 250 is intended toreduce the risk of damage to plunger 240, end cap 236, the sidewall ofhousing 230, or still another component of damper 200 by reducing theforces imparted by plunger 240 as it travels toward an end of stroke.Occupants within a vehicle experience large impulse forces as plunger240 contacts end cap 236 or a component of the suspension system engagesa hard stop. Recoil damper 250 reduces such impulse forces transmittedto occupants within the vehicle by dissipating a portion of the kineticenergy of plunger 240 and shaft 210 (i.e. provide a supplemental dampingforce) as damper 200 reaches an end of stroke (e.g., as the pistonreaches a recoil end of stroke, as the piston reaches a jounce end ofstroke, etc.). According to an exemplary embodiment, recoil damper 250reduces the forces imparted by an obstacle to occupants within thevehicle from 35,000 pounds to 20,000 pounds.

According to an exemplary embodiment, recoil damper 250 dissipatesenergy thereby reducing the total energy of damper 200. As the vehicleencounters a positive obstacle (e.g., a bump, a curb, etc.) or anegative obstacle (e.g., a depression, etc.), the shaft 210 movesrelative to housing 230. Various factors including, among others, thespeed of the vehicle, the weight of the vehicle, and the characteristicsof the obstacle affect the energy imparted into the damper 200 by theobstacle. By way of example, shaft 210 translates toward first end 232of housing 230 as a wheel of the vehicle encounters a negative obstacle.It should be understood that the moving shaft 210 possesses kineticenergy that contributes to the total energy of damper 200. Interactionof recoil damper 250 with plunger 240 dissipates energy thereby reducingthe total energy of damper 200. Such dissipated energy does not increasethe kinetic energy of shaft 210 or plunger 240, according to anexemplary embodiment.

Referring again to the exemplary embodiment shown in FIG. 3 , plunger240 separates the inner volume of housing 230 into a compression chamber260 and an extension chamber 270. As shown in FIG. 3 , housing 230 alsodefines a port, shown as flow port 238. According to an exemplaryembodiment, a fluid (e.g., hydraulic oil, water, a gas, etc.) isdisposed within the inner volume of housing 230. As plunger 240 movestoward first end 232 of housing 230, the pressure of the fluid withinextension chamber 270 increases. According to an exemplary embodiment,the fluid within extension chamber 270 flows outward through flow port238. External valves (e.g. shim valves, etc.) restrict the flow of fluidfrom flow port 238 and provide a base level of damping forces. Such abase level of damping may vary based on the location, speed, or othercharacteristics of plunger 240. According to an exemplary embodiment,damper 200 provides a constant base level damping force as plunger 240translates between first end 232 and second end 234 of housing 230.

According to an exemplary embodiment, recoil damper 250 includes apiston, shown as secondary plunger 252. As shown in FIG. 3 , secondaryplunger 252 is an annular member positioned within extension chamber270. Secondary plunger 252 includes a contact surface that is configuredto engage plunger 240. An opposing surface of secondary plunger 252 isseparated from the contact surface by the thickness of secondary plunger252. According to an exemplary embodiment, secondary plunger 252 iscoupled to an inner sidewall of housing 230 with a seal (e.g., ring,wear band, guide ring, wear ring, etc.), shown as interfacing member254. A recoil chamber 272 is formed by the volume of extension chamber270 located between secondary plunger 252 and end cap 236.

As shown in FIG. 3 , interfacing member 254 is a ring that has acircular cross-sectional shape. According to an alternative embodiment,interfacing member 254 may have a rectangular, square, polygonal, orstill other cross-sectional shape. The interfacing member 254 ismanufactured from a rigid material (e.g., a hard plastic, etc.).According to an exemplary embodiment, the rigid interfacing member 254prevents fluid flow between the inner sidewall of housing 230 andsecondary plunger 252. A rigid interfacing member 254 may also centersecondary plunger 252 within the bore of housing 230 thereby reducingthe likelihood of wear between an outer surface of secondary plunger 252and housing 230. According to an alternative embodiment, interfacingmember 254 is manufactured from another material (e.g., glass reinforcednylon, a nitrile rubber, etc.).

According to an exemplary embodiment, recoil damper 250 includes aresilient member, shown as return spring 256. As shown in FIG. 3 ,return spring 256 extends between a first end that engages secondaryplunger 252 and a second end that engages end cap 236. Return spring 256may be an interlaced wave spring (i.e. a flat wire compression spring),a coil spring, or another type of spring. Return spring 256 positionssecondary plunger 252 within housing 230. The spring force generated byreturn spring 256 may overcome gravity (e.g., where damper 200 ispositioned in a vehicle suspension system with secondary plunger 252above end cap 236) or may position secondary plunger 252 more quicklythan gravity alone (e.g., where damper 200 is positioned in a vehiclesuspension system with secondary plunger 252 below end cap 236, as shownin FIG. 3 ). Return spring 256 is not intended to damp the movement ofplunger 240, and return spring 256 may have a relatively small springconstant (e.g., less than 500 pounds per inch). According to analternative embodiment, recoil damper 250 does not include a returnspring 256. Such a recoil damper may reposition secondary plunger 252using gravity or an alternative device.

According to an exemplary embodiment, secondary plunger 252 defines achannel (i.e. track, depression, kerf, notch, opening, recess, slit,etc.), shown as damping groove 253. As shown in FIG. 3 , damping groove253 extends radially outward across the contact surface of secondaryplunger 252, along an inner cylindrical face of secondary plunger 252,and along the opposing surface of secondary plunger 252. According to analternative embodiment, damping groove 253 extends only along thecontact surface of secondary plunger 252. According to still anotheralternative embodiment, damping groove 253 extends across the contactsurface and along the inner cylindrical face of secondary plunger 252.As shown in FIG. 3 , secondary plunger 252 defines two damping grooves253. According to an alternative embodiment, secondary plunger 252defines more or fewer damping grooves 253. Damping groove 253 is sizedto provide particular flow characteristics. According to an exemplaryembodiment, the channel is defined along an axis extending radiallyoutward from a centerline of secondary plunger 252. According to analternative embodiment, the channel is curvilinear or irregularlyshaped. According to an exemplary embodiment, the channel has a squarecross-sectional shape in a plane that is normal to the axis extendingfrom the centerline of secondary plunger 252. According to analternative embodiment, the channel has another cross-sectional shape(e.g., rectangular, circular, semicircular, parabolic, etc.).

As shown in FIG. 3 , plunger 240 defines a contact surface that engagesthe contact surface of secondary plunger 252. According to an exemplaryembodiment, the contact surface of plunger 240 and the contact surfaceof secondary plunger 252 are complementary (i.e. corresponding, matched,correlative, etc.) thereby reducing the likelihood that pressurizedfluid will seep between recoil chamber 272 and extension chamber 270across the contact surfaces of plunger 240 and secondary plunger 252.According to an alternative embodiment, a seal is positioned betweenplunger 240 and secondary plunger 252.

According to an alternative embodiment, shaft 210 does not extendthrough secondary plunger 252. Such a damper 200 may include a shaft 210that projects toward second end 234 of housing 230 from plunger 240. Alimiter (e.g., a recoil damper) may be positioned between plunger 240and end cap 236. The limiter may provide supplemental damping forces asplunger 240 approaches an end of stroke (e.g., full compression).According to an exemplary embodiment, plunger 240 and second plunger 252are disk shaped. According to an alternative embodiment, plunger 240 andsecond plunger 252 have still another shape.

According to an exemplary embodiment, the various components of damper200 (e.g., the sidewall of housing 230, plunger 240, secondary plunger252, shaft 210, etc.) have a circular cross section. According to analternative embodiment, the various components of damper 200 may includea different cross-sectional shape (e.g., rectangular, square, hexagonal,etc.). While shown in FIG. 3 as having a particular length, width, andthickness, it should be understood that the components of damper 200 maybe otherwise sized (e.g., to suit a particular application).

According to the exemplary embodiment shown in FIGS. 3-4D, plunger 240is actuable within housing 230 from a first location that is offset fromsecondary plunger 252 (e.g., the position shown in FIG. 3 ) to a secondposition where the contact surface of plunger 240 engages with (i.e.contacts, interfaces with, etc.) the contact surface of secondaryplunger 252 (e.g., the position shown in FIG. 4A). As shown in FIG. 4A,plunger 240 translates within housing 230 along a direction of travel280. Such motion may occur, by way of example, as the damper 200approaches an extension end of stroke (e.g., in a recoil motion). Asshown in FIG. 4A, plunger 240 moves along direction of travel 280 suchthat the contact surface of plunger 240 engages the contact surface ofsecondary plunger 252. As the contact surface of plunger 240 engages thecontact surface of secondary plunger 252, the damping groove 253 ofsecondary plunger 252 and the contact surface of plunger 240 form a flowconduit.

According to an alternative embodiment, plunger 240 defines a channel.The channel of plunger 240 may correspond to damping groove 253 ofplunger 240 such that the channel of plunger 240 and damping groove 253of secondary plunger 252 together form a flow conduit. In otherembodiments, the channel of plunger 240 does not correspond to dampinggroove 253 of plunger 240 such that a plurality of flow conduits areformed between the damping groove 253 and the contact surface of plunger240 and the channels of plunger 240 and the contact surface of secondaryplunger 252. According to another alternative embodiment, secondaryplunger 252 does not include damping groove 253, and a channel definedwithin plunger 240 and a contact surface of plunger 240 form the flowconduit.

As plunger 240 translates between the position shown in FIG. 4A to theposition shown in FIG. 4B, fluid flows from recoil chamber 272, betweensecondary plunger 252 and shaft 210, through the conduit defined bydamping groove 253 and the contact surface of plunger 240, through apassage between plunger 240 and the sidewall of housing 230, and intocompression chamber 260. According to an exemplary embodiment, theconduit restricts the flow of fluid from recoil chamber 272 therebydissipating energy and providing a supplemental damping force. Accordingto an exemplary embodiment, damping groove 253 is positioned to reducethe buildup of debris and maintain an unobstructed flow channel alongthe conduit formed by damping groove 253 and the contact surface ofplunger 240. Wear between components of damper 200, oxidation, or stillother conditions may generate debris in the fluid of damper 200. Asshown in FIGS. 3-4D, damping groove 253 is defined across a contactsurface of secondary plunger 252. Fluid flowing through the inner volumeof housing 230 (e.g., due to translation of plunger 240 within housing230) flushes debris from damping groove 253. Such flushing and themovement of shaft 210 relative to secondary plunger 252 reduce the riskof debris obstructing the fluid flow path between recoil chamber 272 andcompression chamber 260 (e.g., between an inner surface of secondaryplunger 252 and an outer surface of shaft 210).

According to an exemplary embodiment, the amount of energy dissipatedand the supplemental damping forces provided by recoil damper 250 (e.g.,due to fluid flow through the conduit) is related to the shape ofdamping groove 253. According to an exemplary embodiment, fluid flowdoes not occur between secondary plunger 252 and the sidewall of housing230. Secondary plunger 252 and interfacing member 254 limit fluid flowbetween recoil chamber 272 and compression chamber 260 to a flow paththrough the conduit. Recoil damper 250 thereby generates a fluid flowpath through the conduit, and interfacing member 254 facilitatesdetermining the expected performance characteristics (e.g., the amountof energy dissipated, the supplemental damping forces provided, etc.) ofrecoil damper 250. Such performance characteristics may be tuned as afunction only of the features of damping groove 253, according to anexemplary embodiment. Limiting fluid from flowing between secondaryplunger 252 and an inner sidewall of housing 230 also provides morepredictable and uniform energy dissipation and supplemental dampingforces (i.e. additional flow paths may introduce additional variabilityinto the energy dissipated by a limiter).

Referring next to FIG. 4C, plunger 240 maintains engagement withsecondary plunger 252 and continues to translate along direction oftravel 280. According to an exemplary embodiment, the end cap 236 is ahard stop for the motion of damper 200 at an end of stroke (e.g.,extension, compression, etc.). As shown in FIG. 4C, end cap 236 is ahard stop for an extension end of stroke for damper 200. According to anexemplary embodiment, the extension forces from plunger 240 and shaft210 are imparted to end cap 236 through secondary plunger 252. Thesecondary plunger 252 and the flow of fluid through the conduit reducesthe magnitude of the extension forces and the total energy imparted oncap 236 by plunger 240 and shaft 210.

According to an exemplary embodiment, end cap 236 includes a contact end237 and has a cylindrical shape that defines an inner volume. Theopposing surface of secondary plunger 252 engages contact end 237 of endcap 236 to limit further movement of plunger 240 and shaft 210 alongdirection of travel 280. It should be understood that return spring 256compresses as plunger 240 and secondary plunger 252 travel toward endcap 236. According to an exemplary embodiment, return spring 256 has anouter diameter that is smaller than contact end 237 of end cap 236 suchthat return spring 256 extends within the inner volume of end cap 236.Return spring 256 nests within the inner volume of cap 236 as plunger240 and secondary plunger 252 translate toward end cap 236 alongdirection of travel 280.

According to an alternative embodiment, a vehicle suspension systemincludes an external hard stop that interfaces with another suspensioncomponent. By way of example, the suspension system may include apolymeric cushion coupled to a chassis of the vehicle that contacts aswing arm. Secondary plunger 252 in such a suspension system may notcontact end cap 236 (i.e. the end of stroke for the installed damper 200may occur before maximum extension). According to an alternativeembodiment, the suspension system includes an external hard stop (e.g.,a polymeric cushion) and also a secondary plunger 252 that engages endcap 236 to distribute the total stopping forces to various suspensioncomponents. According to still another alternative embodiment, damper200 includes another type of internal hard stop (e.g., a snap ringpositioned within and internal groove of housing 230, a stud protrudinginto the inner volume of housing 230, etc.). The internal hard stop mayengage plunger 240, secondary plunger 252, or still another component ofdamper 200.

Referring next to FIG. 4D, plunger 240 translates along direction oftravel 282 and away from secondary plunger 252. By way of example, suchmotion may occur after the vehicle has encountered a negative obstacleas the wheel end begins to travel upward thereby compressing damper 200.According to an alternative embodiment, the motion of plunger 240 awayfrom secondary plunger 252 occurs after the vehicle has encountered apositive obstacle and the wheel end begins to travel downward therebyextending damper 200 (e.g., where recoil damper 250 is incorporated todissipate energy at a jounce end of stroke). Translation of plunger 240along direction of travel 282 increases the pressure of the fluid withincompression chamber 260 and decreases the pressure of the fluid withinrecoil chamber 272 and extension chamber 270. Fluid flows into extensionchamber 270 through flow port 238 as plunger 240 translates alongdirection of travel 282, according to an exemplary embodiment.

As shown in FIG. 4D, the sidewall of housing 230 includes first portionhaving a first diameter and a second portion having a second diameter,the transition between the first diameter and the second diameterforming a shoulder, shown as step 231. According to an exemplaryembodiment, the length of the first portion defines the distance overwhich recoil damper 250 dissipates energy and provides a supplementaldamping force. As shown in FIG. 4D, secondary plunger 252 is coupled tothe first portion with interfacing member 254. As shown in FIG. 4D, thediameter of secondary plunger 252 is greater than the second diametersuch that the secondary plunger 252 translates only within the firstportion of housing 230. Step 231 thereby limits the motion of secondaryplunger 252 and prevents secondary plunger 252 from sliding (e.g., dueto gravity, due to locking forces between secondary plunger 252 andplunger 240, etc.) toward the second end 234 of housing 230. Accordingto an exemplary embodiment, plunger 240 has a diameter that isapproximately equal to the second diameter and is configured totranslate along both the first portion and the second portion of housing230. In some embodiments, plunger 240 is coupled to housing 230 with anintermediate seal.

According to an exemplary embodiment, return spring 256 includes a firstend coupled to end cap 236 and a second end coupled to secondary plunger252. As plunger 240 translates along direction of travel 282, returnspring 256 extends from a contracted position (e.g., nested within endcap 236) to an extended position. According to an exemplary embodiment,the contact surface of secondary plunger 252 engages step 231 whenreturn spring 256 is in the extended position. The extension of returnspring 256 repositions secondary plunger 252 such that recoil damper 250may again dissipate energy and provide a supplemental damping force(e.g., as the vehicle interacts with a subsequent positive or negativeobstacle). As return spring 256 extends, fluid is drawn from extensionchamber 270 into recoil chamber 272 such that fluid is again availableto flow through the conduit, dissipate energy, and provide asupplemental damping force. According to an alternative embodiment,recoil damper 250 does not include return spring 256 and secondaryplunger 252 travels downward toward step 231 due to another force (e.g.,coupling forces between plunger 240 and secondary plunger 252,gravitation forces, etc.).

As shown in FIG. 4D, translation of plunger 240 along direction oftravel 282 from the position shown in FIG. 4C separates plunger 240 fromsecondary plunger 252. According to an alternative embodiment, plunger240 maintains engagement with secondary plunger 252 until secondaryplunger 252 engages step 231. According to an exemplary embodiment,damping groove 253 facilitates separation of plunger 240 from secondaryplunger 252 as plunger 240 translates along direction of travel 282.Damping groove 253 reduces the risk that coupling forces will lockplunger 240 to secondary plunger 242 (e.g., due to contact between thetwo otherwise smooth corresponding surfaces). Such coupling forces mayotherwise result in the translation of secondary plunger 252 along thelength of housing 230 with plunger 240, the combination of secondaryplunger 252 and plunger 240 providing supplemental damping forces inunintended stroke positions (e.g., in locations other than at an end ofhousing 230, etc.).

Referring next to the exemplary embodiment shown in FIGS. 5-6 , adamper, shown as damper assembly 300, includes a manifold 310 coupled toa body portion 320 with a shaft 330. As shown in FIG. 5 , manifold 410includes an interface, shown as joint 311, that is configured to engagea portion of the vehicle (e.g., the chassis, a hull, etc.). The bodyportion 320 defines an interface 322 that is configured to engageanother portion of the vehicle (e.g., a lower swing arm, etc.).According to an exemplary embodiment, damper assembly 300 is a coaxiallyintegrated double damper that facilitates the spring force compensationstrategy while providing damping forces that vary based on the positionof the damping piston.

As shown in FIG. 6 , damper assembly 300 includes a base damper assembly(i.e. an inner damper assembly), shown as primary damper 340, and asupplemental damper, shown as secondary damper 360. According to anexemplary embodiment, the primary damper 340 provides roll control andbase damping through an inner damper circuit and the secondary damper360 provides position dependent damping through an outer dampingcircuit. The secondary damper 360 provides damping forces that areindependent of those provided by primary damper 340. According to anexemplary embodiment, the damping forces provided by secondary damper360 are negligible in conditions where the primary damper 340 alone isdesigned to provide damping forces. The damper assembly 300 includes alimiter, shown as recoil damper 500, that is configured to engage thesecondary damper 360. According to an exemplary embodiment, recoildamper 500 dissipates energy and provides a supplemental damping force.As shown in FIG. 6 , the primary damper 340 and the secondary damper 360are integrated into a single unit thereby reducing the size and weightof damper assembly 300. According to an exemplary embodiment, theprimary damper 440 and the secondary damper 460 are positionedcoaxially, which further reduces the size of damper assembly 440 (e.g.,relative to two dampers positioned in parallel).

According to an exemplary embodiment, the primary damper 340 includes afirst tubular member 342 positioned within a second tubular member 344.As shown in FIG. 6 , a first piston, shown as plunger 346 is coupled toan end of first tubular member 342 and second tubular member 344. Theprimary damper 340 includes a third tubular member 348 at leastpartially surrounding the second tubular member 344. An aperture, shownas aperture 349, extends through a sidewall of the third tubular member348. According to an exemplary embodiment, plunger 346 is slidablycoupled to an inner surface of third tubular member 348. A cap 350 and acap 352 are coupled to opposing ends of third tubular member 348. Asshown in FIG. 6 an outer surface of second tubular member 344 ispositioned within an aperture defined by cap 352.

As shown in FIG. 6 , the secondary damper 360 includes a housing, shownas housing 370, a second piston, shown as plunger 362, and a tubularmember 364. A cover, shown as bellow 365, is disposed around tubularmember 364 to prevent debris from entering body portion 320 or manifold310. According to an exemplary embodiment, housing 370 defines aplurality of apertures, shown as openings 372. According to an exemplaryembodiment, conduits hydraulically couple a portion of the openings 372to other openings 372 thereby forming at least one hydraulic circuit.

According to an exemplary embodiment, the tubular member 364 ispositioned coaxially with the first tubular member 342 and the secondtubular member 344. An end cap 366 is coupled to an end of housing 370,and the tubular member 364 is slidably coupled between the cap 352 andthe end cap 366. According to an exemplary embodiment, plunger 362 hasan annular shape that defines an aperture extending therethrough. Theplunger 362 is disposed between an inner surface of the housing 370 andan outer surface of third tubular member 348. As shown in FIG. 6 , anaperture, shown as aperture 345, extends through a sidewall of thesecond tubular member 344. It should be understood that the componentsof damper assembly 300 may have various cross-sectional shapes (e.g.,cylindrical, rectangular, square, hexagonal, etc.). According to anexemplary embodiment, the components of damper assembly 300 are coupledwith seals (e.g., bushings, wear bands, o-rings, etc.) that areconfigured to prevent pressurized fluid from passing between thechambers discussed herein or leaking out of damper assembly 300.

Referring again to FIG. 6 , primary damper 340 and secondary damper 360define a plurality of flow channels. According to an exemplaryembodiment, primary damper 340 defines a compression chamber 380 that isformed by an inner surface of third tubular member 348, cap 350, an endof first tubular member 342, and a first face of plunger 346. A flowchannel 382 is defined by an inner surface of first tubular member 342from the compression chamber 380, through manifold 310, and through afirst flow port 312. According to an exemplary embodiment, the primarydamper 340 includes an extension chamber 384 defined by an inner surfaceof tubular member 364, a second face of plunger 346, a portion ofplunger 362, and a face of cap 352. It should be understood thataperture 345 and aperture 349 facilitate the formation of extensionchamber 384 by placing various internal chambers in fluid communication.A flow channel 386 is defined by an inner surface of second tubularmember 344, an outer surface of first tubular member 342, manifold 310,and a second flow port 314. According to an exemplary embodiment, theflow channel 382 and the flow channel 386 form the inner damper circuit.An inner surface of the housing 370, cap 350, an outer surface of thirdtubular member 348, and a first surface of plunger 362 define asecondary compression chamber 390, and the inner surface of the housing370, end cap 366, an outer surface of tubular member 364, and a secondsurface of plunger 362 define a secondary extension chamber 392.

Extension and retraction of the damper assembly 300 provides relativemovement between a first set of components (e.g., plunger 346, firsttubular member 342, second tubular member 344, tubular member 364, endcap 366, etc.) relative to a second set of components (e.g., housing370, cap 350, third tubular member 348, cap 352, etc.). Such extensionand retraction causes fluid to flow through the flow channel 382 andflow channel 386 in opposite directions (e.g., fluid flows intocompression chamber 380 and out of extension chamber 384 as the damperassembly 300 is extended). According to an exemplary embodiment, thearea of plunger 346 and the area of first tubular member 342 exposed tocompression chamber 380 is approximately equal to the area of plunger346 and the area of plunger 362 that are exposed to extension chamber384 thereby providing a one-to-one working area ratio.

Extension and retraction of the damper assembly 300 also providesrelative movement between plunger 362 and housing 370. According to anexemplary embodiment, plunger 362 is coupled to plunger 346 (e.g., withtubular member 364, manifold 310, and first tubular member 342). Asdamper assembly 300 is compressed, fluid is forced from secondarycompression chamber 390, through a first set of openings 372 to a secondset of openings 372 via a conduit, and into a secondary extensionchamber 392. As damper assembly 300 is extended, fluid is forced fromsecondary extension chamber 392, through a first set of openings 372 toa second set of openings 372 via a conduit, and into secondarycompression chamber 390. Fluid is forced through specific openings 372based on the position of plunger 362 within housing 370. Certain sets ofopenings may be deactivated (e.g., due to hydraulic lock, because a setof the openings is obstructed by plunger 362, etc.). According to anexemplary embodiment, valves (e.g., bidirectional flow valves, etc.) maybe positioned within the conduits that couple the openings 372.According to an exemplary embodiment, secondary damper 360 providesdamping forces that vary based on the position of plunger 362 and thedirection that plunger 362 is traveling.

Referring to the exemplary embodiment shown in FIGS. 7-11 , recoildamper 500 is positioned between plunger 362 and end cap 366. As shownin FIG. 7 , recoil damper 500 includes a piston, shown as secondaryplunger 510. According to an exemplary embodiment, secondary plunger 510includes an annular body member 512 that has a contact surface 514, aninner cylindrical face 515, and an opposing surface 516. As shown inFIG. 7 , contact surface 514 and opposing surface 516 are separated by athickness of annular body member 512. The recoil damper 500 includes aresilient member, shown as return spring 520. As shown in FIG. 7 ,return spring 520 extends between a first end that engages secondaryplunger 510 and a second end that engages end cap 366. Return spring 520may be an interlaced wave spring (i.e. a flat wire compression spring),a coil spring, or another type of spring. Return spring 520 positionssecondary plunger 510 within housing 370, according to an exemplaryembodiment. According to an exemplary embodiment, secondary plunger 510is coupled to an inner sidewall of housing 370 with a seal (e.g., ring,wear band, guide ring, wear ring, etc.), shown as interfacing member518. A recoil chamber 393 is formed by the volume of secondary extensionchamber 392 located between secondary plunger 510 and end cap 366.

According to an exemplary embodiment, secondary plunger 510 defines achannel (i.e. track, depression, kerf, notch, opening, recess, slit,etc.), shown as damping groove 519. As shown in FIG. 7 , damping groove519 extends radially outward across contact surface 514 of secondaryplunger 510. According to an alternative embodiment, damping groove 519extends radially outward across contact surface 514 and along innercylindrical face 515. According to still another alternative embodiment,damping groove 519 extends radially outward across contact surface 514,along inner cylindrical face 515, and across opposing surface 516. Asshown in FIG. 7 , secondary plunger 510 defines a single damping groove519. According to an alternative embodiment, secondary plunger 510defines a plurality of damping grooves 519.

As shown in FIG. 8A, the sidewall of housing 370 includes first portion374 having a first diameter and a second portion 376 having a seconddiameter, the transition between the first diameter and the seconddiameter forming a shoulder, shown as step 378. According to anexemplary embodiment, the length of first portion 374 defines thedistance over which recoil damper 500 dissipates energy and provides asupplemental damping force. As shown in FIG. 8A, secondary plunger 362is coupled to the first portion with an interfacing member 518. As shownin FIG. 8A, the diameter of secondary plunger 510 is greater than thesecond diameter such that the secondary plunger 510 translates onlywithin first portion 374 of housing 370. Step 378 thereby limits themotion of secondary plunger 510 and prevents secondary plunger 510 fromsliding (e.g., due to gravity, due to locking forces between secondaryplunger 510 and plunger 362, etc.) toward an opposing end of housing370. According to an exemplary embodiment, plunger 362 has a diameterthat is approximately equal to the second diameter and is configured totranslate along both first portion 374 and second portion 376 of housing370. In some embodiments, plunger 362 is coupled to housing 370 with anintermediate seal.

Plunger 362 translates toward end cap 366 along direction of travel 363as damper assembly 300 is extended. As shown in FIGS. 8A-8B, secondaryplunger 510 is biased by return spring 520 into engagement with step378. According to an exemplary embodiment, plunger 362 engages secondaryplunger 510, forces secondary plunger 510 from step 378, and compressesreturn spring 520. The pressure of fluid disposed within recoil chamber393 is increased as secondary plunger 510 translates along direction oftravel 363. The fluid from recoil chamber 393 flows between secondaryplunger 510 and tubular member 364, through a conduit formed by dampinggroove 519 and a contact surface of plunger 362, between first portion374 and plunger 362, and into secondary compression chamber 390.

According to an exemplary embodiment, the conduit restricts fluid flowthereby dissipating energy and providing a damping force. As damperassembly 300 extends, plunger 362 and secondary plunger 510 translatealong direction of travel 363 toward end cap 366. According to anexemplary embodiment, end cap 366 is a hard stop for damper assembly300. As shown in FIG. 11 , plunger 362 and secondary plunger 510translate along direction of travel 363 until a surface of secondaryplunger 510 contacts end cap 366. Return spring 520 nests within end cap366 as secondary plunger 510 translates along direction of travel 363.It should be understood that return spring 520 forces secondary plunger510 toward step 378 as plunger 362 translates away from end cap 366thereby repositioning secondary plunger 510 to again interact withplunger 362 during a supplemental end of stroke event.

Referring next to the exemplary embodiment shown in FIGS. 12-15 , apiston, shown as plunger 600, includes an annular body member 610 thathas a contact surface 612, an inner cylindrical face 614, and anopposing surface 616. According to an exemplary embodiment, plunger 600is implemented as part of a limiter for a suspension component. As shownin FIGS. 12 and 14 , contact surface 612 includes an outer annularportion that is parallel to opposing surface 616 and an inclined portionthat is angled relative to the outer annular portion of contact surface612. The inclined portion extends radially inward and toward opposingsurface 616 from the outer annular portion of contact surface 612. Achannel, shown as groove 620, is defined within an outer annular surfaceof annular body member 610 (e.g., to receive a seal, etc.).

As shown in FIG. 12 , plunger 600 includes a channel (i.e. track,depression, kerf, notch, opening, recess, slit, etc.), shown as dampinggroove 630, extending radially outward from a centerline of annular bodymember 610 across contact surface 612. According to an alternativeembodiment, damping groove 630 extends radially outward across contactsurface 612 and along inner cylindrical face 614. According to stillanother alternative embodiment, damping groove 630 extends radiallyoutward across contact surface 612, along inner cylindrical face 614,and across opposing surface 616.

Damping groove 630 is configured to interface with a contact surface ofa plunger and form a conduit to dissipate energy and provide dampingforces. As shown in FIG. 15 , damping groove 630 is parallel to theinclined portion of contact surface 612. According to an exemplaryembodiment, plunger 600 defines a single damping groove 630. Accordingto an alternative embodiment, plunger 600 a plurality of damping grooves630. Damping groove 630 is sized to provide particular flowcharacteristics. According to an exemplary embodiment, damping groove630 is defined along an axis extending radially outward from acenterline of annular body member 610. According to an alternativeembodiment, damping groove 630 is curvilinear or irregularly shaped.According to an exemplary embodiment, damping groove 630 has a squarecross-sectional shape (e.g., 0.020 inches square) in a plane that isnormal to the axis along the length of damping groove 630. According toan alternative embodiment, damping groove 630 has anothercross-sectional shape (e.g., rectangular, circular, semicircular,parabolic, etc.).

The construction and arrangements of the damper, as shown in the variousexemplary embodiments, are illustrative only. Although only a fewembodiments have been described in detail in this disclosure, manymodifications are possible (e.g., variations in sizes, dimensions,structures, shapes and proportions of the various elements, values ofparameters, mounting arrangements, use of materials, colors,orientations, etc.) without materially departing from the novelteachings and advantages of the subject matter described herein. Someelements shown as integrally formed may be constructed of multiple partsor elements, the position of elements may be reversed or otherwisevaried, and the nature or number of discrete elements or positions maybe altered or varied. The order or sequence of any process, logicalalgorithm, or method steps may be varied or re-sequenced according toalternative embodiments. Other substitutions, modifications, changes andomissions may also be made in the design, operating conditions andarrangement of the various exemplary embodiments without departing fromthe scope of the present invention.

What is claimed is:
 1. A damper assembly, comprising: a tubular memberincluding a sidewall and a cap positioned at an end of the sidewall, thesidewall and the cap defining an inner volume, wherein the sidewallcomprises a first portion fixedly coupled with a second portion of thesidewall, wherein the first portion and the second portion define ashoulder of the sidewall; a rod extending within the inner volume; aprimary piston positioned within the inner volume and coupled to therod, the primary piston defining a first contact surface; and asecondary piston having a second contact surface, an opposing secondsurface, and an inner face that receives the rod, the second contactsurface forming a passage extending between the inner face and an outerperiphery of the secondary piston, wherein the primary piston and thesecondary piston separate the inner volume into a first working chamber,a second working chamber, and a recoil chamber; and wherein the firstcontact surface and the passage are configured to cooperatively define aflow conduit upon engagement between the primary piston and thesecondary piston; wherein the second contact surface is configured toengage the first contact surface such that an open flow path is formedfrom the recoil chamber through (i) an aperture of the secondary pistonand (ii) the flow conduit, upon engagement between the primary pistonand the secondary piston.
 2. The damper assembly of claim 1, wherein theprimary piston is moveable within the tubular member between a firstlocation, an intermediate location, and an end of stroke, and whereinthe primary piston is configured to maintain engagement with thesecondary piston between the intermediate location and the end ofstroke.
 3. The damper assembly of claim 1, wherein the recoil chamber isdefined between the opposing second surface of the secondary piston andthe cap.
 4. The damper assembly of claim 2, wherein the damper assemblyprovides a base level of damping as the primary piston moves between thefirst location and the intermediate location and an increased level ofdamping as the primary piston moves between the intermediate locationand the end of stroke.
 5. The damper assembly of claim 1, furthercomprising a resilient member disposed between the secondary piston andthe cap and thereby positioned to bias the secondary piston into directengagement with the shoulder.
 6. The damper assembly of claim 5, whereinthe first portion is circular and has a first diameter and the secondportion is also circular and has a second diameter, wherein the firstdiameter is greater than the second diameter, and wherein a transitionbetween the first portion and the second portion defines the shoulder.7. The damper assembly of claim 6, wherein a diameter of the primarypiston is less than the second diameter such that the primary piston isextendable along a length of the tubular member.
 8. The damper assemblyof claim 1, wherein the aperture of the secondary piston is a centralaperture positioned at a central portion of the secondary piston,wherein the rod extends through the central aperture.
 9. A damperassembly, comprising: a housing having an end cap and defining an innervolume, the housing comprising a first portion fixedly coupled with asecond portion, wherein a transition between the first portion and thesecond portion defines a shoulder; a primary piston positioned withinthe housing; and a limiter positioned between the primary piston and theend cap, the limiter comprising: a damper piston having a contactsurface, an opposing second surface, and an inner face, the primarypiston and the damper piston separating the inner volume into a firstworking chamber, a second working chamber, and a recoil chamber; and arod coupled to the primary piston and extending past the inner face;wherein the contact surface defines a passage extending between theinner face and an outer periphery of the damper piston, wherein theprimary piston and the passage are configured to cooperatively define afirst flow conduit upon engagement between the primary piston and thedamper piston; and wherein an aperture of the damper piston defines asecond flow conduit, and wherein the first flow conduit and the secondflow conduit cooperate to define an open flow path from the recoilchamber.
 10. The damper assembly of claim 9, further comprising aresilient member disposed within the recoil chamber, between theopposing second surface of the damper piston and the end cap, theresilient member thereby positioned to bias the damper piston intodirect engagement with the shoulder.
 11. The damper assembly of claim 9,wherein the primary piston, the first portion, and the second portionhave circular cross-sectional shapes, wherein the first portion has afirst diameter and the second portion has a second diameter, wherein thefirst diameter is greater than the second diameter, and wherein thetransition between the first portion and the second portion defines theshoulder.
 12. The damper assembly of claim 11, wherein the diameter ofthe primary piston is less than the second diameter such that theprimary piston is extendable along the length of the housing.
 13. Thedamper assembly of claim 9, wherein the aperture of the damper piston isa central aperture positioned at a central portion of the damper piston.14. The damper assembly of claim 13, wherein the rod extends through thecentral aperture of the damper piston.
 15. The damper assembly of claim9, wherein an end of the rod is coupled to the primary piston.
 16. Thedamper assembly of claim 9, wherein the primary piston is moveablewithin the housing between a first location, an intermediate location,and an end of stroke, and wherein the primary piston is configured tomaintain engagement with the limiter between the intermediate locationand the end of stroke.
 17. The damper assembly of claim 16, wherein thedamper assembly provides a base level of damping as the primary pistonmoves between the first location and the intermediate location and anincreased level of damping as the primary piston moves between theintermediate location and the end of stroke.
 18. The damper assembly ofclaim 9, wherein the recoil chamber is defined between the opposingsecond surface of the damper piston and the end cap.
 19. A damperassembly, comprising: a housing having an end cap and defining an innervolume, wherein the housing comprises a first portion fixedly coupledwith a second portion of the housing, wherein a transition between thefirst portion and the second portion defines a shoulder of the housing;a primary piston positioned within the housing; and a limiter positionedbetween the primary piston and the end cap, the limiter comprising: adamper piston having a contact surface, an opposing second surface, andan inner face, the primary piston and the damper piston separating theinner volume into a first working chamber, a second working chamber, anda recoil chamber; and a rod coupled to the primary piston; wherein thecontact surface defines a passage extending between the inner face andan outer periphery of the damper piston; wherein the damper pistondefines an inner passage; and wherein the primary piston and the passageare configured to cooperatively define a flow conduit upon engagementbetween the primary piston and the damper piston; and wherein the flowconduit and the inner passage cooperate to define an open flow path fromthe recoil chamber.
 20. The damper assembly of claim 19, wherein thefirst portion has a first diameter and the second portion has a seconddiameter, wherein the first diameter is greater than the seconddiameter, and wherein the transition between the first portion and thesecond portion defines the shoulder and wherein the diameter of theprimary piston is less than the second diameter such that the primarypiston is extendable along the length of the housing.